This invention relates to conveyor ovensxe2x80x94especially, but not exclusively, to pizza ovensxe2x80x94and more particularly to ovens having high efficiency heat supplies.
Conveyor ovens are well-known appliances for cooking or baking food products, especially pizzas, or the like. One example of such an oven is shown in U.S. Pat. No. 5,277,105.
Conventionally these ovens have large stainless steel housings with heated cavities in the form of tunnels extending through them. An endless conveyor extends through and out the opposite ends of the tunnel in order to transport food products through the heated cavity at a speed which cooks or bakes them during transit. Heretofore, the heat delivery system has included relatively expensive space-consuming motors, blowers, and ducts which supplied heat from a plenum through metal fingers and passageways which are also made of stainless steel. The metal fingers constitute air flow channels that deliver streams of hot air which impinge upon the surfaces of the food products on the conveyor. A control panel having microprocessors associated therewith enables the user to regulate the heat, speed of conveyor, etc. to select a temperature and transit time appropriate to the food product being transported through the oven.
The design, development and production of such conveyor ovens require a substantial capital investment. When there is an improvement of the oven which requires additional space in the housing, there is an advantage in making the existing parts smaller in order to obtain the additional space needed without requiring further significant capital investment resulting from redesign of the entire oven.
Another consideration in the design of conveyor ovens is the cost of energy. As the cost of energy increases, the efficiency of the heat delivery system raises to or near the top of the various considerations that go into the design of a conveyor oven. This means that a heating system for an oven which was acceptable when energy was less expensive may prove impractical, or at least undesirable, as the cost of energy goes up.
Yet another of the considerations which goes into the design of a conveyor oven is the simplicity of the design, the ease of control and maintenance, reliability and the like. Also, it is desirable to make such products with less-complicated components.
Still another consideration is the need to meet applicable government regulations and industry standards in the various locations where the oven is used and, more particularly, to universally meet as many of such regulations and standards as possible. For example, in the U.S., natural gas is a principal source of fuel for the conveyor oven. Other countries may rely primarily upon propane. In Europe, for example, mixtures of gases are often used, with different ratios of the gases in the mixture being used in different countries. Also, gas is a potentially hazardous substance; therefore, almost everywhere, the various governments have established their own safety regulations. Therefore, providing a universally usable oven design is highly desirable, but can be challenging.
Accordingly, an object of the invention is to provide a more compact, space-saving, and efficient heat delivery system for a conveyor-type oven. Another object is to provide an oven that is universally usable in many different locations throughout the world. Here, an object is to simplify controls, construction, and maintenance and to make a conveyor oven which is less complex. In this connection, an object is to accomplish these and other objects at reduced costs and improved efficiency.
In keeping with an aspect of the invention, these and other objects are accomplished by designing the heating system to eliminate the burner, blower and ducts used heretofore in a forced-draft system and to replace them with inshot burners that use an induced-draft system which does not require blowers specially dedicated to providing combustion air. The space saved by an elimination of such components makes for a more compact and efficient heat delivery system. With the present invention, the fan or blower used to circulate hot air within the oven is the only fan or blower that is required. A modulating gas valve is used to closely control the efficient flow of gas to the burner.